1. Field of the Invention
The invention relates generally to systems and methods for production from open-hole wellbores having multiple zones within. In more particular aspects, the invention relates to production systems that are useful for gravel packing and isolating separate zones within an open-hole wellbore and which allow monitoring of wellbore conditions within the separate zones.
2. Description of the Related Art
Hydrocarbon production wellbores often extend through a number of separate zones within the earth. These zones are separated by layers of relatively impermeable rock. The individual zones may contain oil, gas, water, or a mixture of these fluids. It is desirable to isolate the individual zones within the wellbore to prevent movement of fluids between the zones within the wellbore, which could lead to contamination of the fluids being produced. This isolation is accomplished by creating a blockage within the wellbore between the production tubing string and the walls of the wellbore. Typically, the blockage is created by setting a packer within the wellbore.
Many current wellbore production systems have “open-hole” wellbores, wherein a portion of the wellbore is not lined with casing. Open-hole systems are prone to collapse along their uncased portions. Sand screens and gravel-packing are used to try to prevent this, as well as prevent sand production. For isolation of zones within an open-hole system, a packer assembly is needed that can provide large radial expansion of the sealing element. Unfortunately, conventional large expansion packer systems generally lack the ability to pass electrical or fiber optic cables or fluid conduits axially through the packer assembly so that other devices may be used below the packer device. The desirable requirements for a large diameter packer system are typically at odds with those for a conduit pass-through system. U.S. Pat. No. 6,220,362, issued to Roth et al. describes a pass-through conduit arrangement for a packer assembly or other tool. The Roth patent is owned by the assignee of the present invention and is incorporated herein by reference. Roth describes a system wherein one or more axial conduit passages are formed through an interior portion of a packer or other tool. Roth teaches that there be complete pressure isolation between the conduit and both the tubing and the annulus. However, Roth describes the use of a separate carrier 60 that lies radially within the tool mandrel 24 and is used to define the longitudinal passages for the conduits or cables. The potential exists for improper sealing between the carrier and mandrel during fabrication of the tool, leading to undesirable fluid entry into the longitudinal passages. Additionally, this design does not offer any means for radial communication of fluid outwardly from the flowbore of the tool to the radial exterior of the tool. In fact, the requirement that the longitudinal passages remain isolated from fluid pressure from the flowbore, as well as the annulus, dictates against penetration of the carrier and/or mandrel by a radial fluid communication passage. If the carrier and mandrel of this tool were perforated to allow radial fluid communication, the passages defined therebetween would undesirably become exposed to external wellbore fluid pressures.
To the inventor's knowledge, conduit feed through systems have not been successfully integrated into hydrostatically-set packer assemblies. It is believed that this failure is due to the complexity of a hydrostatic setting mechanism and the need for such a device to communicate hydrostatic fluid pressure through the inner mandrel of the packer assembly and into a chamber within the exterior portion of the packer assembly. The use of multiple interior pieces, such as a separate carrier and mandrel, to define a longitudinal cable/conduit pass-through, and the attendant assembly requirements, also adds to the difficulty of incorporating a cable feed-through feature into a hydrostatically-set device.
U.S. Pat. No. 6,842,315 issued to Coronado et al., describes a hydrostatically-set packer device having a composite sealing element with large radial expansion capabilities for use in through tubing and open hole applications. This patent is owned by the assignee of the present invention and is, therefore, incorporated by reference. The device of the '315 patent provides no feed-through arrangement for cables or conduits to be passed longitudinally through the packer device.
A further problem with the use of conventional production assemblies in open-hole, multi-zonal wellbores is that it is difficult to monitor the temperature and pressure of the separate zones. Once conventional packers are set between individual zones, there is no communication through the annulus across the packers. Thus, temperature, pressure or other conditions within a particular zone cannot be monitored within the annulus. This makes controlled production from individual zones much more difficult.
U.S. Pat. No. 6,854,522, issued to Brezinski et al. describes a system for setting a series of expandable isolators (packers) within an open-hole wellbore between individual zones. However, this system lacks any means for monitoring temperature, pressure or other conditions within the individual zones. In addition, the system lacks any means for communication of power or data across the isolators within the annulus.
The present invention addresses the problems of the prior art.